A touch panel usually includes a touch sensing electrode and a touch sensing circuit. The touch sensing electrode is used to sense a touch event and provide a sensed voltage. The touch sensing circuit (also called the reading circuit) is used to read the sensed voltage by converting the sensed voltage into an electrical signal which can be easily processed by a subsequent processing circuit.
Due to factors such as manufacturing processes, temperatures and aging of elements, characteristic parameters of elements (e.g., the threshold voltage of a transistor) in the touch sensing circuit are apt to drift, thereby causing errors in the reading of the voltage by the sensing circuit. This may cause an erroneous sensing of the touch event.